Bilateral Interface Engineering for Efficient and Stable Perovskite Solar Cells Using Phenylethylammonium Iodide

Achieving high efficiency and long-term device stability is a vital issue for the commercialization of organic-inorganic hybrid perovskite solar cells (PeSCs). In this work, phenylethylammonium iodide (PEAI)-induced bilateral interface engineering was developed to improve the device efficiency and stability of methylammonium lead triiodide (MAPbI₃)-based PeSCs. Introducing PEAI onto a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layer modifies the surface properties of PEDOT:PSS and facilitates the formation of a high-quality perovskite active layer with enlarged grains on PEDOT:PSS. PEA⁺ in PEAI-PEDOT:PSS also alters the work function of PEDOT:PSS, leading to a reduction in the energy difference between the PEDOT:PSS and MAPbI₃ perovskite layers, which decreases the energy loss during charge transfer. Additionally, depositing PEAI onto three-dimensional (3D) perovskite yields a two-dimensional/three-dimensional (2D/3D) stacked structure for the perovskite active layer. Because the two-dimensional (2D) top layer acts as a capping layer to prevent water penetration, the stability of the perovskite active layer is significantly enhanced. A PeSC device fabricated based on this combination exhibits enhanced power conversion efficiency (PCE) and an extended device lifetime compared to a pristine PeSC. Under high-humidity conditions (75 ± 5%), the PEAI-treated PeSC retains 88% of its initial power conversion efficiency (PCE) after 100 h. In contrast, a pristine PeSC device loses over 99% of its initial PCE after only 25 h under the same conditions.